Bayonet style turn-signal bulb won't twist in

Anybody else encountered this problem? Probably has something to do with fixture being 50 years old. I’ve always installed this style bulb before with no problem, by pressing in and twisting to lock the bayonet. But no matter how hard I press (within limits of not breaking glass bulb) it won’t twist. I’m guessing whatever allows you to press the bulb inward is stuck. I tried silicone grease & a dose of PB Blaster, let it sit overnight, still a no go. I’m thinking maybe

  • Heat it w/hot air gun
  • Remove fixture from truck and disassemble/clean gunk on work bench

Any other ideas?

Or replace the socket.

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Single filament? Then I’d look into a new socket. Dual filament, make sure you’re putting the offset lugs in the correct way.


Yes, dual filament. Offset tabs (lugs) are oriented correctly, one lower, one higher. The problem is the tabs on the bulb are both too high to move into their slots. If I could push the bulb in 1-2 mm or so, then it would slide into slot. I’m guessing there are springs on the spherical gadgets that mate up with the bulb’s connection, and the springs aren’t moving. How is the socket replaced? Is that accessed from the rear of the fixture?

It looks sort of like this

Turn it 180 degrees. One of the bayonet pins sits closer to the base than the other, you may have it backwards. Im assuming 1034 or 1157 bulb.

Yes, 1157. The pins are indeed offset, but by inspection look to be oriented correctly. But I’ll try it 180 degrees just to make sure. I suppose it is possible it is the wrong bulb for the package, not an actual 1157.

Operator error, wrong bulb, or does it say made in China? Maybe try a new brand but just use dielectric grease not silicone so it works when you finally get it in.

I’ve always thought dielectric grease, silicone grease , and plumber’s grease are different names for the same thing.

You’re the engineer but I have separate containers of each. One for brakes, another for sockets, and another for faucets. Plus I have bulb grease for 110v bulbs. I’m happy.

How did you get the old bulb out?

This may or may not apply to your case, but I’ve had a particular brand of bulb not fit, but the same type of bulb from another brand did fit. Can’t remember what the problem brand was, but it just didn’t seem to have the right configuration. I have no idea whether this is relevant to your problem but just thought I’d pass my experience on since it was sort of an unexpected thing to deal with.

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I’ve also run into this where the ball(s) of solder on the base were larger and protruding more than they should be. Filing a small amount off still allowed for proper connection once the lamp was installed.

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Broke the glass then pulled the base out with pliers.

That method, along with heat, another dose of lube (silicone spray), and wrapping the bulb w/duct tape for better grip finally did the trick.

I confirmed the two corresponding balls inside the socket were free, bobble heads on springs, but there must be something else wrong with either the socket or the bulb, b/c needed way more than the normal amount of pushing force for pins on bulb base to clear the socket tabs.

While the filing & above finally allowed the bulb to twist in, of course two problems remain. First, bulb now doesn’t make a tight fit in socket; not a very good connection on one of the filaments. Slight reverse twist on the bulb made for w/pretty tight fit with both filaments working though. Second, it was bear to remove the duct tape from the bulb … lol …

While the turn signal lights now work, I’m not satisfied with result. I plan to replace the entire fixture on both sides (reflecting cup, gaskets & socket) when good weather returns.